Switching of high-voltage electric apparatus (such as circuit breakers) can generate high-frequency voltage and/or current excursions, also called “spikes” or “bursts”. These excursions can penetrate through instrument transformers and the corresponding secondary wiring to protective device inputs, distorting the relay input signals. While many protective devices filter higher frequencies, the distorted relay input signals caused by power excursions cannot be entirely eliminated. As such, the power excursions can penetrate through the relay filters as one or multiple power spikes superimposed on the measured signal. As a result, distorted relay input signals can cause erroneous operation of the protective device. This phenomenon can especially be a problem for fast-operating protective devices, such as differential relays.